The Study On Selective Modification Of Cocatalysts To Enhance The Photocatalytic Performance Of Single-crystal Bismuth Vanadate

Constructing a highly efficient photocatalytic system is of great significance for achieving environmental remediation and alleviating the energy crisis.Among various semiconductor materials,BiVO₄ has attracted widespread attention in photocatalytic degradation of organics and O₂ evolution owing to its abundant raw material sources,appropriate band gap?2.4 eV?and positive position of its valence band edge?2.43 V vs.NHE?.Unfortunately,for pure BiVO₄,the rapid recombination of photogenerated electron-hole pairs and the weak reduction ability of photogenerated electron which attributes to the relatively positive position of its conduction band edge?0.03 V vs.NHE?,have severely limited its practical application in photocatalysis.Recent researches have demonstrated that coupling crystal-facet engineering with selective interface modification is an effective strategy to achieve rapid separation and transport of photogenerated carriers and effective interfacial catalytic reaction.The article mainly focuses on the synthesis,morphological structure characterization,photocatalytic degradation of organics and mechanism of the single-crystal BiVO₄ photocatalytic materials with selective modification of cocatalysts:?1?the facile synthesis of Ag₂O-Ag selectively modified on single-crystal BiVO₄;?2?the photocatalytic synthesis of low-cost Cu selectively loaded on single-crystal BiVO₄;?3?the selective photodeposition of hole cocatalyst FeOOH on single-crystal BiVO₄.The results are as follows:First,the single-crystal BiVO₄ photocatalyst was prepared through a facile hydrothermal process,and Ag₂O-Ag was successfully loaded on the?010?facet of single-crystal BiVO₄ to synthesize the Ag₂O-Ag/BiVO₄ photocatalyst by the photodeposition of Ag and the in situ surface oxidation by low-temperature calcination.It was found that the Ag2O-Ag/BiVO4 photocatalyst showed nearly comparable activity with Pt/BiVO₄ and obviously higher activity than pure BiVO₄and Ag/BiVO₄.The enhanced activity of Ag₂O-Ag/BiVO₄ can be possibly ascribed to the excellent synergistic effect of crystal-facet engineering of BiVO₄ and selective modification of Ag₂O-Ag;namely,the photogenerated charges can be spatially separated between different facets of BiVO₄,while the selectively loaded Ag₂O-Ag can achieve effective interfacial transfer and catalytic reaction of photogenerated electrons.Second,discovering selective modification of low-cost and highly effecient electron cocatalysts on semiconductor is of great significance.In this study,Cu nanoparticles with low cost were successfully modified on the?010?facet of single-crystal BiVO4 to synthesize Cu/BiVO4 photocatalyst by a photodeposition method.The photocatalytic results indicated that Cu/BiVO₄ showed significantly higher activity than pure BiVO₄ photocatalyst by photocatalytic decolorization of MO aqueous solution.When the amount of Cu was 1 wt%,the Cu/BiVO₄?1 wt%?achieved the highest photocatalytic activity(0.0719 min^-1).The improved photocatalytic performance can be possibly attributed to the coupling strategy of combining crystal-facet engineering of BiVO₄ with selective deposition of Cu cocatalyst,which can restrict the recombination of photogenerated carriers,accelerate the interfacial transfer and catalytic reaction of photogenerated electrons.Third,selective modification of low-cost and highly efficient hole cocatalyst on photocatalyst is one of the most effective methods to improve the reaction in photocatalysis.In this study,hole cocatalyst FeOOH was selectively loaded on the?110?facet of single-crystal BiVO4 to synthesize FeOOH/BiVO4 photocatalyst by a photodeposition process via using FeSO₄ as Fe precursor with the presence of Cu?NO₃?₂ in water.The photocatalytic results showed that FeOOH/BiVO₄?3 wt%?exhibited the highest activity by photocatalytic decolorization of MO aqueous solution,and its rate constant was 0.0884 min^-1.Moreover,Pt nanoparticles were selectively loaded on the?010?facet of FeOOH/BiVO₄?3 wt%?through the photodeposition method,and the prepared Pt-FeOOH/BiVO₄ photocatalyst further showed enhanced photocatalytic activity.The improved photocatalytic performance of FeOOH/BiVO₄ can be possibly explained as the synergistic effect of crystal-facet engineering of BiVO₄ and selective modification of hole cocatalyst FeOOH,which surpresses the recombination of photogenerated carriers and speeds up the transfer and catalytic reaction of photogenerated holes.